You'll struggle to see a Starlink with the naked eye in a populated area. The star I could barely see seems likely to be Arcturus, which is a fairly bright one, but the ISS is about a hundred times brighter than that. A magnitude of around 0 for Arcturus and about -5 for the ISS, depending on the angles of things at the time.
One of those numbers that I remember, 2.51188, the fifth root of 100, the difference between one magnitude and the next one up or down.
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